Boom rigging



Oct. 20, 1970 J. 0. WEST 3,534,869

BOOM RIGGING Original Filed Sept. 29,1967

3 Sheets-Sheet 1 o J: I, m g INVENTOR JOHN D. WEST 1970 J. 0. WEST 3,534,869

BOOM RIGGING' Original Filed Sept. 29. 1967 5 Sheets-Sheet 3 INVENTOR JOHN D. WEST Och 1970 r r J. 0. WE T 3,534,869

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United States Patent ice 3,534,869 BOOM RIGGING John D. West, Manitowoe, Wis., assignor to The Manitowoc Co., Inc., Manitowoe, Wis., a corporation of Wisconsin Continuation of application Ser. No. 671,813, Sept. 29, 1967. This application Aug. 29, 1969, Ser. No. 856,882 Int. Cl. B66c 23/62 US. Cl. 212-144 Claims ABSTRACT OF THE DISCLOSURE This invention comprises rigging for supporting boom structure in which the angle between a primary support structure and the boom structure is increased by the use of a member spacing the primary support structure away from the boom structure. To minimize the tendency of such an arrangement to bend the boom structure into a downwardly convex configuration, an auxiliary support structure is connected to the lower chords of the boom structure thereby counteracting the tendency of the boom structure to bow as well as minimizing tensile loads in the lower chords. Since the primary and auxiliary support structures are concurrently tensioned during the raising of the boom structure, the tendency of the boom structure to bow is offset in large part by the action of the auxiliary support structure.

This application is a continuation of Ser. No. 671,813 filed Sept. 29, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to boom rigging used in the raising and lowering of boom structure and particularly to boom rigging adapted to minimize the loading and bowing of the boom structure because of the forces necessarily imparted thereto during the raising and lowering thereof.

Load supporting boom structures of the type used in equipment, such as cranes, draglines, and the like, are generally mounted adjacent one end portion thereof by a hinge arrangement on a stationary or mobile base support and are equipped with rigging to alter the inclination of the boom structure with respect to the ground in order to perform the various functions for which the equipment is made. The trend of recent years is to provide longer and longer boom structures in order to meet the requirements and demands of construction and excavation problems.

One of the most severe loading situations to which a boom structure is subjected occurs when the boom is raised from a horizontal position to an inclined position from which the load is actually handled. Accordingly, it is desirable to minimize the loading of the boom structure during the raising operation if one is to succeed in providing industry with boom structures of the length desired.

One facet of the problem of minimizing the load on a boom structure during the raising and lowering operations resides in the fact that the primary support structure, which extends from adjacent the base support to adjacent the boom point, necessarily describes a rather small angle with respect to the boom structure. Because of the small angle, a significant amount of the forces imparted to the primary support structure results in the loading of the boom structure rather than in producing a moment tending to rotate the boom about the hinge point.

Another facet of the problem of minimizing the load on a boom structure during the raising and lowering operations resides in the fact that the boom structure tends Patented Oct. 20, 1970 to bow into a downwardly convex configuration as disclosed in US. Pat. 3,072,265. As will become clearer as the discussion progresses, these facets are interrelated because the greater the force applied to the primary support, the greater will be the tendency to bow into the downwardly convex configuration.

Because of the use of a pivoted link separating the primary support structure from the boom structure, the interrelation of these facets of the problem becomes more intimate and more complex. More specifically, the use of the pivoted link aggravates the tendency to bow thereby making especially desirable an additional or auxiliary support structure constructed and arranged to minimize bending or bowing.

It has been found that the auxiliary support structure of the instant invention, when taken alone, has proved advantageous in producing boom structure of greater lengths. The advantages of the auxiliary support structure, when used alone, occur in a slightly different context. Because the auxiliary support structure is connected to the lower chords of the boom structure, it has acted to reduce thetensile forces often found in the lower chords. This has enabled the outer segment of the boom structure to be cantilevered from the zone to which the auxiliary support structure is attached.

It is an object of the instant invention to provide boom structure equipped with primary support structure for producing a moment tending to rotate the boom structure about the hinge point and a member spacing an intermediate portion of the primary support structure away from the boom structure thereby increasing the angle between the boom structure and the primary support structure.

Another object of the instant invention is to provide boom structure having primary support structure and a spacing member of the type described wherein there is further provided auxiliary support structure connected to the lower chord or chords of the boom structure for minimizing the bowing or bending of the boom structure.

Still another object of the instant invention is to provide boom structure having primary support structure arranged to produce a moment tending to rotate the boom structure about the hinge point wherein there is further provided an auxiliary support structure connected to the lower chord or chords of the boom structure allowing the boom structure to be cantilevered from a point intermediate the end portions thereof.

Other objects and important features of the invention will be apparent from a study of the specification following taken with the drawing, which together show, illustrate, describe and disclose a preferred embodiment or modification of the invention and what is now considered to be the best mode of practicing the principles thereof. Other embodiments or modifications may be suggested to those having the benefit of the teachings herein, and such other modifications or embodiments are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevational view of a crane equipped with boom structure and rigging according to the principles of the instant invention;

FIG. 2 is a simplified view of the crane of FIG. 1 illustrating the boom structure in the horizontal position;

FIG. 3 is a simplified view of the crane of FIG. 1 showing the boom structure in a first inclined position;

FIG. 4 is simplified view of the crane of FIG. 1 illustrating the boom structure in a greater inclined position;

FIG. 5 is a simplified view of the crane of FIG. 1 showing the boom structure in a very nearly vertical position;

FIG. 6 is a force diagram of prior art boom construction taken at the boom point at the start of the boom raising operation;

FIG. 7 is a force diagram of the boom construction of the instant invention taken at the boom point at the start of the boom raising operation;

FIG. 8 is a simplified force diagram of prior art boom construction taken at a center section of the boom at the start of the boom raising operation;

FIG. 9 is simplified diagram of the forces and resultants produced on a center section of the boom by the primary and auxiliary support structures at the start of the boom raising operation;

FIG. 10 is a simplified force diagram of the boom construction of the instant invention taken at a center section of the boom at the start of the boom raising operation;

FIG. 11 is a schematic View of the forward end of the boom structure illustrating the maximum angle between the primary support structure and the boom centerline;

FIG. 12 is a simplified force diagram of a central portion of the boom structure when using the auxiliary support structure without using a member for spacing the primary support from the boom structure; and

FIG. 13 is a cross-sectional view of the boom structure of FIG. 1 taken along line 13-13 thereof as viewed in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is now directed to FIG. 1 of the drawing wherein there is shown a machine or equipment in the form of a crane 10 having an elongate jib-less boom structure 12 hingeably connected to a base support comprised of an upper works 14 by a hinge structure 16 with the boom 12 extending therefrom and terminating in a boom point 18. According to conventional practice, the boom 12 may comprise a plurality of insert sections 20 each of which is provided with one or more upper chords 22 and one or more lower chords 24 interconnected by a plurality of lacing elements 26 and diagonal lacing elements 27.

A gantry 28 is pivotally mounted to the upper works 14 and carries a suitable back hitch pendant 30 secured as at 32 to the upper works 14. The back hitch pendant 30 is preferably comprised of a plurality of pivoted links or a bodily flexible member, such as a cable or wire rope, and constitutes a limit upon the amount of upward pivotal movement of the gantry 28. A suitable gantry lifting assembly 34 is pivotably mounted to the upper works 14 and includes a roller 36 for contacting the gantry 28. The gantry lifting assembly 34 also comprises a power element 38 such as a fluid cylinder 38 for rotating the gantry lifting assembly 34 so that the roller 36 engages the gantry 28 and acts to rotate the gantry 28 into the position shown in FIG. 1.

A bodily flexible member 38, such as a wire rope or cable, is wound between a plurality of sheaves 40 on the terminal portion of the gantry 28 and suitable sheaves 41 mounted on the end portion of a mast 42 pivotally connected adjacent the upper works 14 and preferably to the boom structure 12.

Depending on the requirements of the equipment, both ends of the flexible member 38 may terminate and be attached to a pair of suitable drums 44 within the upper Works 14 or one end portion of the flexible member 38 may be affixed to either the gantry or the mast 42. In any event it will be apparent that the operation of the drum 44 will act to pivot the mast 42 for purposes to be more fully described hereinafter.

A load hoist cable 46 is provided which is Wound about a hoist drum (not shown) in the upper works 14 and passes over a plurality of guides 48 to sheaves 50 secured adjacent the boom point 18 in order to carry any load L being handled by the crane 10.

Boom rigging or boom support structure 52 is provided for supporting the boom 12 during the operation thereof for movement between a substantially horizontal position to a substantially vertical position as illustrated in FIGS. 2-5. The boom rigging 52 is comprised of a member or structure 54 pivotally connected by a hinge structure 56 to the upper chords 22 intermediate the ends of the boom structure 12 and a bodily flexible primary support structure 58 having a first segment 60 leading from the member 54 to the mast 42 and a second segment 62 leading from the member 54 to the boom point 18.

As shown best in FIG. 13, the member or structure 54 comprises a rigid frame pivoted to the upper chords 22 of the boom structure 12 by the hinge structure 56. As will be appreciated from a comparison of FIGS. 1 and 13, the first and second segments 60, 62 preferably comprise a multipart connection between the mast 42 and the member 54.

Each of the primary support structure segments 60, 62 are comprised of a plurality of elongated bodily flexible pendant bridles 64, 66 respectively which are connected in end-to-end relation by a pluarlity of connectors 68, 70. The lower ends of the first segment is connected to the mast 42 by any suitable mechanism 72, which preferably provides for the adjustment of the length of the segment 60, such as a turnbuckle or the like. Another connecting mechanism 74 connects the upper ends of the first segment 60 to the upper end portion of the member 54, as shown in FIGS. 1 and 13.

In much the same manner, a pair of connecting mechanisms 76, 78 connect the second primary support structure segment 62 to the member 54 and to the boom point 18 respectively. It will be readily apparent that the adjustment of the turnbuckles 72, 76 will vary the lengths of the segment 62, 64 and will also change the angle of inclination of the member 54 with respect to the boom structure 12 at a location 88 generally vertically downafter, this adjustment may be performed to achieve the greatest possible angle between the second segment 62 and the centerline of the boom structure 12 consistent with the remaining configuration of the device.

The boom rigging 52 also comprises auxiliary support structure 80 made of a plurality of pendant bridles 82 secured together by a number of connectors 84. The lowermost end portion of the auxiliary support structure 80 is aflixed adjacent the end portion of the mast 4.2 by a suitable connecting mechanism 86, such as a turnbuckle or the like. The upper end of the auxiliary support structure 80 is affixed to the lower chord 24 of the boom structure 12 at a location 88 generally vertically downwardly from the hinge connection 56 when the boom structure 12 is located in the horizontal position as may be seen in FIG. 2. Although the securement of the upper end of the auxiliary support may be done With an adjustable mechanism, this connection is illustrated to be non adjustable.

For the sake of brevity, in the above description and disclosure, only one element of the auxiliary support structure 80 has been mentioned, but it is to be understood that corresponding elements and accessories are provided for the auxiliary support 80 in laterally spaced relationship relative to each other on each side of the crane 10 and the boom 12.

It is understood that apparatus other than the crane 10 may be provided with the improved boom rigging of this invention and in such instances the auxiliary rigging assembly 80 may be anchored to a base from which the boom 12 may be pivoted in the manner as described above with reference to the upper Works 14 of the crane 10.

The effect of the boom. rigging 52 on the boom structure 12 may be noted from an inspection of FIGS. 2-5 wherein there is illustrated, in solid lines, the boom 12 having the boom rigging 52 while in dotted lines a centerline 190 of a conventional boom is illustrated for the purpose of comparison. It is to be noted that the centerline 190 describes an appreciable amount of normal downward bow or natural deflection due to the weight of the structure while the boom 12, which is provided with the member 54 and the auxiliary support structure 80, has a controlled bow or downward deflection which is materially reduced.

The reduction in bowing of the boom 12 is thought to be the result of two factors. The first factor is the lessening of the tension in the primary support 84 allowed by increasing the angle between the primary support 54 and a centerline 90 of the boom structure 12. This factor may best be explained by a comparison of FIGS. 6 and 7. As shown in FIG. 6 the angle or between the primary support 114 and the boomcenterline 190 is rather small thereby requiring a large force F to produce the needed moment R to rotate the conventional boom structure about its hinge point. As a result of the large force F 21 large load R is created which has the effect of loading the boom structure.

On the other hand, FIG. 7 shows an angle ,8 between the primary support segment 62 and the boom centerline 90 which is substantially greater than the angle on. In order to achieve the same moment R tending to rotate the boom structure 12 about the hinge point 16, a much smaller force F is required thereby producing a smaller load R and consequently loading the boom structure 12 to a lesser degree. Accordingly, a boom structure equipped with the boom rigging described herein may be made of a longer length because of a lesser tendency to load the boom because of the forces transmitted by the primary support structure '58.

The difficulty created by the use of the primary support structure 58 and the member '54 lies in the imposition of a downward load in the center of the boom structure 12 thereby aggravating the tendency to how. This, of course, is created by the load transmitted to the upper chords of the boom structure 12 through member 54 tending to create a greater bow in the boom structure.

As shown in FIG. 8, a conventional boom having upper and lower chords is bowed by the load L thereby placing a compressive load L, on the upper chord and placing a tensile load L, on the lower chord.

The resultant forces transmitted to the boom structure 12 by the member 54 and the auxiliary support structure 80 may be seen in FIG. 9 wherein L denotes the load transmitted to the boom structure 12 by the primary support 58 and the member 54. L denotes the load transmitted to the boom structure 12 by the auxiliary support 80. As mentioned previously, the load L tends to how the boom structure 12 but is offset by the load L transmitted to the boom structure 12 by the auxiliary support 80'. Another resultant produced by the load L on the lower chords 24 is a compressive load L acting thereon. Since the lower chord 24 is in tension during the raising opera tion, the imposition of the compression load thereon tends to diminish chord stress.

From the previous discussion it will be readily apparent that it would be unwise to attach the auxiliary support structure 80 to the upper chords 22 since this would impose a compressive load thereon thereby aggravating the situation already present in the upper chords during the raising operation.

FIG. illustrates a simplified version of what is thought to be the loading situation at the center of the boom structure 12 adjacent the connections of the member 54 and the auxiliary support structure 80. It will be noted that the compressive loads in the upper chords 22, denoted P are less than that in the conventional boom structure of FIG. 8. This result is achieved because of the lesser force F needed to produce the moment necessary to rotate the boom structure 12 about the hinge point 16. It will also be noted that the tensile loads, designated as F,,, in

the lower chords 24 are much less than that shown for the conventional boom structure. This is thought to be the effect of the lesser force F needed to create the desired moment for rotational movement of the boom structure 12 and the compressive load transmitted to the boom structure 12 by the auxiliary support structure 80.

FIG. 10 also reveals that the bending load, designated as P is not greatly diiferent than the bending load in the conventional boom structure depicted in FIG. 8. The straightening load F on the lower chord is, of course, transmitted to the boom structure 12 from the auxiliary support and further acts to minimize the bending of the boom structure 20 since it counterbalances the bending load on the upper chords.

FIG. 11 illustrates that the greatest, and most desirable, angle between the second segment 62 and the boom centerline occurs when the member 54 is perpendicular to the second segment 62 when the boom structure is in the horizontal position. This may be achieved by adjusting the turnbuckles 72, to alter the length of the support segments 60, 62.

As shown in FIGS. 2-5, the winding of the flexible member 38 about drum 44 during the raising operation acts to pivot the mast 42 in a counterclockwise direction thereby raising the boom structure 12. As will be noted, the centerline 112 of the conventional boom structure will describe a greater bow during any circumstance than will the boom structure 12.

While the invention has been described and disclosed in terms of an embodiment which it has assumed in practice, the scope of the invention should not be deemedto be limited by the precise embodiment herein shown, illustrated, described and disclosed and it is to be understood that other such embodiments are intended to be reserved, especially as they fall within the scope of the claims herein subjoined.

What is claimed is:

1. In a crane having an upper works; an elongate boom, pivotally mounted to the upper works, having upper chord means and lower chord means; means carried by the upper works for tensioning a primary support to raise the boom; and a bodily flexible primary support operative between one location adjacent the boom top and a second location on the retracting means; the improvement comprising a member connected to the upper chord means intermediate the boom ends and spacing an intermediate portion of the primary support further away from the boom than a line defined by the two locations to increase the angle between the primary support and the boom at the top thereof; and

means for reducing the bow imparted to the boom during raising thereof, the last mentioned means comprising an auxiliary support connected to the lower chord means intermediate the ends of the boom; and means tensioning the auxiliary support during raising of the boom.

2. The crane of claim 1 wherein the member is pivotally connected to the upper chord.

3. The crane of claim 1 wherein the member and the auxiliary support are connected to the boom at locations such that an imaginary plane perpendicular to the centerline of the boom intersects both locations.

4. The crane of claim 1 wherein the boom comprises a plurality of lower chords and the auxiliary support comprises a component connected to each lower chord.

5. The crane of claim 1 wherein the means tensioning the primary support comprises a mast pivotally mounted on the crane, the primary support being secured to the mast; and

means for moving the mast about the pivot thereof.

6. The crane of claim 5 wherein the auxiliary support is connected to the mast, the mast comprising the means tensioning the auxiliary support.

7. The crane of claim 5 wherein the mast is pivotally mounted on the boom adjacent the lower end thereof.

8. In a crane having a base; a boom, pivotally mounted to the base, having a boom point; a movable member associated with the crane for tensioning a primary sup port to raise the boom; and a primary support extending from a location on the movable member to a location adjacent the boom point; the improvement comprising a member disposed intermediate the ends of the boom for spacing an intermediate portion of the primary support away from the boom beyond a line defined by the locations to increase the angle between the primary support and the boom point; and

means for reducing the bow imparted to the boom during raising thereof, the last mentioned means comprising an auxiliary support extending from adjacent the base support to an intermediate portion of the boom; and means tensioning the auxiliary support concurrently with raising of the boom. 9. The crane of claim 8 wherein the boom comprises References Cited UNITED STATES PATENTS 763,222 6/1904 Driessche 212-47 2,309,715 2/1943 RudoW 212144 2,609,940 9/1952 Grunduig 212-l44 2,869,735 1/1959 Page 212144 3,072,265 1/1963 Nickles 21258 3,176,854 4/1965 Brown 212-144 HARVEY C. HORNSBY, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5343369 Dated October 20, 1970 Inventor-(S) John D. West It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, lines 39-+Oz Change "structure 12 at a location 88 vertically downafter, this" to --structure 12.

As will be pointed out more fully hereinafter,

this--.

Suki; m9 SBILED OE c 29 6EAL) Afloat:

Edward 1m Fletcher, Ir.

mtingofficer 

